Smog hangs in the air around buildings in the Luohu district of Shenzhen. Photo: Bloomberg

Desperate times call for desperate measures.

"It's a perfectly natural response when you are confronted with a problem," said Gong Zhiqiang in Beijing, a mechanical engineer who spends his nights fine-tuning his designs for amateur air filters.

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After Gong posted his prototypes online in 2012, requests flooded in for step-by-step instructions. Obsessing over air, he said, has become a nationwide pastime.

The urgent search for ways to alleviate pollution has been spurred by the problem's growing visibility as well as the public's increased access in recent years to hourly measurements of the filth they're breathing.

Chinese cities have some of the world's most polluted air. The haze is often so thick it blots out the sun. On especially bad days in cities such as Harbin, in northeast China, residents can't even see across the street. Airports struggle regularly to land planes in thick fog. A study published in the British medical journal the Lancet attributed 1.2 million premature deaths in 2010 to bad air.

Other countries have cut air pollution by limiting emissions from factories and cars. China's leaders have been reluctant to sacrifice economic growth, and state-run industries have used their economic clout to resist stricter rules.

So people have looked to more novel ideas.

In the western city of Lanzhou - deemed by the World Health Organization as having the worst air in China - officials have proposed digging gullies into surrounding mountains. Others have talked in recent years of levelling mountains altogether. But the ideas, requiring mountain-sized funding, have stalled.

On the sci-fi end of the spectrum, a Dutch artist is designing a giant electrostatic "vacuum cleaner''. The device - which resembles a giant hula hoop - uses an electrified wire to attract smog particles. The artist's firm says it has successfully tested prototypes. In an online video demonstrating the concept, the machine miraculously cuts a small circle in the city's haze to reveal blue skies and a shining sun.

"It's not going to cure smog on a large scale, but at least we can remind people what clean air looks like," said artist Daan Roosegaarde. He said Beijing's mayor has shown interest. Beijing officials declined to comment, but the Dutch Embassy, which has been assisting Roosegaarde, confirmed that he has meetings scheduled with Beijing officials next month.

But what's garnered the most attention in recent weeks is confirmation that the Chinese government is researching the use of artificial rain to rinse out bad air.

A document released by China's Meteorological Administration in November said that all local weather officials would be able by 2015 to use artificial rain to clear away smog. Shortly after, in a closed meeting, Beijing's vice mayor told subordinates his city was researching the method, according to state-run media.

Bloggers reacted with equal parts surprise, jokes and scepticism. Officials in the city and Meteorological Administration have refused to elaborate further. Reached by phone, a Beijing government spokesman confirmed the vice mayor's comment but declined to say more.

In many ways, the idea is unsurprising. Because of China's chronic water shortages, it has invested heavily in artificial rain since the late 1950s. The country boasts the world's largest rainmaking force, with 6902 cloud-seeding artillery guns, 7034 launchers for chemical-bearing rockets, more than 50 planes and 47,700 employees, according to a 2012 government tally.

The massive infrastructure was most famously deployed in Beijing to ensure clear skies for the opening ceremony of the 2008 Olympics.

But applying rainmaking to smog is a relatively new idea. Several scientists at government think tanks and universities declined a journalist's requests this month to discuss it. Such information remains, like many things in China, under the tight control of the government.

According to the few scientists who were willing to talk, as well as explanations in state-run media, the science involves using rockets, cannons or planes to sow clouds with catalysts such as dry ice, silver iodide and salt powder. The substances augment the clouds' natural rainmaking processes.

The resulting rainfall in theory scavenges polluting particles from the air through a process called "wet deposition."

But the plan has serious flaws, many experts say.

The right moisture conditions are needed for cloud-seeding to work. The location of a city's largest concentration of pollution must be determined. And the rainfall can be fickle and difficult to aim.

"It's complicated. Scientists here can't even agree on how much rainfall cloud-seeding actually causes," said Wang Shaowu, a retired atmospheric professor at Peking University. "Say you have 20 millimetres of rain did 5 millimetres come from artificial methods or 15 millimetres?"

Then there's the matter of unintended side effects.

Whatever chemicals go up to seed the clouds eventually come down, said Zhao Lijian, a pollution expert at the Energy Foundation, a nonprofit group that promotes clean energy. "You're also sending all those heavy pollutants in the air into the water system."

And there's the issue of stealing rain from other areas where it might have fallen.

The only real solution to China's pollution problems, Zhao and other scientists stress, is to cut emissions from its power plants, factories and cars. But that is hugely difficult.

It would mean cutting into China's heavy dependence on coal-burning electrical plants. It also would require taking on powerful state-owned industries, such as China's oil and power companies, which have long resisted stricter environmental controls.

But Chinese leaders recently unveiled an ambitious $US280 billion plan that includes limiting coal use and banning high-polluting vehicles.

Salivating at the prospects, Western clean-technology companies are stampeding to sell China solutions. A US Department of Commerce analysis has predicted that China's clean-tech market will reach $US555 billion by 2020.

The market has benefited small-scale vendors such as Gong, who has sold more than 40 of his homemade air filters in the past two years.

As he and his wife have talked about having a baby, he's begun thinking about pollution problems their child might face.

"I want to design a really good mask for children," he said. "I've got a few ideas already."